8/26/2015 4:15 AM
Edited Date/Time: 8/26/2015 4:18 AM
First, get the desired fabric. Choose a part that has no stitches and appeals to you. Wrap the fabric around the whole seat and 'secure' it in place with rubber bands, zip ties, small rope… Get the scissors and cut a small slit into one of the sides of the thing, slightly above the rubber band line. From there, cut around the whole fabric.

Then, leave the cloth hanging on the seat and trim it away. Scissors need to be very sharp. Trim mostly the sides. You need to leave about 2 to 3 cm overhang.

With your fingers and a screwdriver, fold up the cloth and get it into the area that will be covered by the cover. Don't forget that the nut hole has got to be visible.

Get the front plastic cover and screw it in about two turns. Pry the cloth into the slot between the seat and the cover with a flat head screwdriver. Screw it some more and repeat until the nose of the seat looks legit and the fabric is tight.

No wrinkles and sweet as hell, here is the front end:

Now move to the rear of the seat and do the same thing. With your fingers, get the cloth 'in-to da zone'.

Screw it in… Pry the cloth in with screwdriver… Tighten… Pry… Etc. It has gotta be clean ad sweet looking with no wrinkles at the back, okay honeypot?

KAZAM! You have done 80 % of the job. You need a good two sided adhesive to continue from now on, one that STICKS like a pit bull on a poodle.
Get one side of the tape and stick it in the insides of the seat edge. Then, stretch the cloth a final time to get all the wrinkles out, take the backing out, and put that bugger on!!!

Do the same for the other side. You will end up with this bad boy:

TAADAA! There it is, as simple as that. Take a cutter, or better yet, a sharp surgical doctor grade knife and make a slit into the fabric ( hole for allen key for the pivotal bolt). If you want, you can mark the place with a slit, take the whole cover out and sew a patch of rubber from an old tube to make it nicer. Chances are that you are not going to do so.
Here is what a pivotal seat cover looks like when it's not on the seat. PS: With a LOT of wrinkles too.

If you want to make it a bit more serious and definitive, you need to get the staples from the old seat cover out, and unstitch the parts. Then, play 'em over your new cloth and cut them to size. Sew them together and replace. It's more straightforward. And, assuming that it's gonna be a good job, don't forget to use that old tube under the bed and to make a pivotal bolt hole slot thingamajig. If your cloth is light and not heavy duty, you might wanna sew another layer under.
Just my two cents on the whole thing. Please try it out guys. This takes a maximum of 30 minutes and changes the look of the seat for nothing at all. Let's see some others!
It doesn't matter where a train goes. It's decidin' to get on that does.